This research will develop and test interventions to improve the nutrition and physical activity environment for obesity and CVD prevention in Wisconsin American Indian (Al) children. It will build on previously successful NARCH collaborations and community-based participatory research with 3 Wisconsin tribes, the Great Lakes Inter-Tribal Council and the University of Wisconsin. This project will 1) test the effectiveness of a mentored home-visiting and group support intervention to improve nutrition and physical activity levels in Al preschoolers and their primary caregivers vs. intervention materials alone, 2) involve each community in detailed assessments of the macro-level community environmental supports and barriers to families for achieving healthy diets and adequate levels of physical activity, and 3) incorporate participatory research throughout all stages of the project to develop additional data-driven, culturally acceptable community based interventions to support healthy behavior changes in families and increase community research capacity. Aim 1, Healthy Children Strong Families (HCSF), is a 2 year randomized controlled trial composed of one year of targeted home visits during which trained Al mentors will work with 3-5 year old Al children and their primary caregivers to promote skill-based behavior change. During year 2, intervention families will attend monthly group meetings with activities to sustain changes made in year 1. Control families will receive intervention materials and newsletters only. 75 Al families will comprise each of the two arms of the study. Primary outcomes are decreased child waist circumference and decreased caregiver body mass index. Secondary outcomes include: increased fruit/vegetable consumption, decreased TV viewing, increased physical activity, decreased soda/sweetened drink consumption, improved caregiver biochemical indices, and increased caregiver self-efficacy to adopt healthy behaviors. Aim 2, Supportive Communities, utilizes community advisory boards to design and prioritize assessments of food, recreation, economic, legal, and other systems in their communities. These boards will apply focus groups, surveys, GIS mapping and direct observation in their evaluations. Outcomes include: committed community advisory boards, community assessment reports and intervention projects. Aim 3, Participatory Process, assesses the advancement of the participatory research process toward increasing levels of community research involvement and capacity. Training and resources in obesity prevention will be adapted into a number of tribal settings and programs to enhance sustainability. This project will move the academic and tribal partnership along the spectrum of community-based participatory research to the next level of collaboration. Ultimately, this multilevel project should reduce morbidity and mortality from obesity and its sequelae in a population of high-risk American Indian children. It will also lay the foundation for future collaborative research efforts.